The present disclosure relates to a self-steering vehicle.
A typical representative of such a self-steering vehicle is what is referred to as an autonomous lawnmower (ARM) such as is known for a wide variety of purposes, in particular for domestic use. Such a self-steering device usually operates according to the principle of random navigation: this means that the ARM usually travels straight ahead until it meets a barrier (sensed by means of a sensor system or a border wire) and then turns at a randomly determined angle. Such a procedure is simple in terms of control technology and is, in particular, implemented without mapping (map data) of the surface to be worked on (working area), but this known procedure has in practice the disadvantage that complete (surface) coverage in accordance with the directions which are respectively traveled along in accordance with the angle is random, with the result that complete coverage is not ensured or only takes place after a very large number of route movements. This then leads again to disadvantageous redundancy in the form of multiple traversing.
It is also known from the prior art to allow a self-steering vehicle, for example an autonomous lawnmower, to travel over the working area on the basis of existing map data. However, a condition for this is usually a navigation system which is accurate (according to the mapping or a movement resolution) and which either causes a very large amount of expenditure, for example in the form of customary GPS technologies (and is therefore not very suitable, in particular, for a cost-sensitive domestic application) or else does not permit sufficient positional resolution for working on, in particular, relatively small surfaces.
In addition, it is known from the prior art to delimit the working area by means of a border wire (through which a current flows). Magnetic field sensors which are assigned to the ARM are then able to determine, through detecting the border wire signal (for example modulated onto the border wire), whether the ARM is inside or outside the boundary defined by the wire.
However, a particular challenge is not only to detect the border wire as such but also to detect a current position of the vehicle (ARM) along this border wire (which is typically closed since it completely surrounds a working area): such a procedure which detects when a starting point is reached when the vehicle travels along a boundary contour without a precise positioning or locating system is known from WO 03/039314. This prior art stores data items about the path traveled along at regular intervals during the travel process, wherein current data items are respectively compared with stored information in order to determine whether the same data items are present. However, the detection is based on the comparison of a current block of constant length (L) with a stored block of the same length; the method which is known from the prior art is therefore based on the fact that the characteristic of a block of this length is sufficient to identify the block unambiguously within the entire contour.
However, in practice, this is problematic because, in particular, simple contours such as, for example, a rectangular lawn surface already point to the obvious problem that the block of the length (L) will occur repeatedly. In addition, since further data items and peripheral conditions which could prevent such ambiguities are often not present on simple surfaces, this procedure is potentially subject to problems and requires improvement, not least because maps created in the known way can otherwise have critical errors.